A study of the sensitivity of long-range passive ranging techniques to atmospheric scintillation

Abstract

This work aims to quantify and improve the sensitivity of monocular passive ranging techniques in sequences that are degraded by the the quasi-periodic inter frame motion and localised blurring associated with atmospheric scintillation. Ranges from tens of meters up to 1km in uncontrolled outdoor conditions were investigated. This work has application in surveillance, border control, artillery, and the autonomous navigation of ground vehicles. A field trial with long focal length, large aperture cameras was held. The targets were placed at known distances and a scintillometer was used to measure the turbulence between the cameras and each target. A variety of depth from defocus and depth from focus algorithms were applied to a the video sequences to determine range to the targets. Increasing levels of atmospheric turbulence were observed ranging from no turbulence to mild, moderate and severe turbulence. Algorithms for the mitigation of atmospheric turbulence were applied to the recorded video sequences. The passive ranging techniques were then applied to the turbulence-mitigated video sequences and the results compared to that of the raw sequences. Finally, findings regarding the best performing combination of ranging and mitigation techniques to use under different scintillation conditions are presented.